pub fn ec_select<F: PrimeField, FC>(
chip: &FC,
ctx: &mut Context<F>,
P: EcPoint<F, FC::FieldPoint>,
Q: EcPoint<F, FC::FieldPoint>,
sel: AssignedValue<F>
) -> EcPoint<F, FC::FieldPoint>where
FC: FieldChip<F> + Selectable<F, FC::FieldPoint>,